Facility-Level Resilience Analysis of Urban Flood Defense Systems

The increasing frequency and intensity of urban flooding, driven by rapidly changing climate patterns, necessitate the enhancement of the resilience of flood defense infrastructure. Urban infrastructures, as forms of complex systems, are interconnected through multi-scale subsystems with dynamic feedback mechanisms, which influence their resilience based on the adaptive cycle stage of each subsystem. Despite this, existing studies predominantly focus on macro-level analyses, underscoring the need for resilience studies at the facility scale, which supports large-scale flood defense operations. Traditional flood defense infrastructures, designed based on historical rainfall patterns, often fail to address the variability introduced by climate change. These systems are further compromised by aging and inadequate maintenance, which diminishes their functional capacity. This study proposes a novel approach to quantitatively evaluate the resilience of flood defense facilities. The proposed resilience assessment integrates both structural factors, such as design capacity, and non-physical factors, including regulatory frameworks and institutional mechanisms. Using the 4Rs framework—Robustness, Redundancy, Resourcefulness, and Rapidity—a comprehensive evaluation model was established for flood defense infrastructures, including sewer systems, pumping stations, and detention basins. Analytical Hierarchy Process (AHP) analysis was conducted to validate the indicators and determine appropriate weights for each parameter within the mathematical resilience function, which adopted a sigmoid model to integrate key parameters, such as initial performance, performance variability, recovery speed, and time. Additionally, a simulation-based approach was employed to predict recovery and failure scenarios. The simulation examined the impact of fixed and randomly varying resilience indicators on recovery outcomes. Results demonstrated that disaster frequency and intensity significantly influence failure probabilities and recovery thresholds. Recovery thresholds, defined as the minimum performance levels below which facilities fail to restore their initial capacity, provided critical insights into the functional limits of the infrastructure. The study further evaluated recovery success by tracking performance curves over time. This methodology highlights the actual recovery capacity of urban flood defense facilities. The findings offer predictive insights into whether these facilities can recover under repeated disaster conditions or transition to alternative stable states, contributing to enhanced flood response capabilities of urban infrastructure.

Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Ministry of Science and Technology (RS-2024-00356786) and Korea Environmental Industry & Technology Institute grant funded by the Ministry of Environment (RS-2023-00218973).